title: cAMP phosphodiesterase inhibitors increases nitric oxide production by modulating dimethylarginine dimethylaminohydrolases.
abstract: BACKGROUND
  Pulmonary arterial hypertension is characterized by a progressive increase in pulmonary vascular resistance caused by endothelial dysfunction, inward vascular remodeling, and severe loss of precapillary pulmonary vessel cross-sectional area. Asymmetrical dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, and its metabolizing enzyme dimethylarginine dimethylaminohydrolase (DDAH) play important roles in endothelial dysfunction. We investigated whether combined phosphodiesterase (PDE) 3 and 4 inhibition ameliorates endothelial function by regulating the ADMA-DDAH axis.
  
  
  RESULTS
  We investigated the effects of the PDE3/4 inhibitor tolafentrine in vitro on endothelial cell survival, proliferation, and apoptosis. Effects of tolafentrine on the endothelial nitric oxide synthase/nitric oxide pathway, DDAH expression, DDAH promoter activity, and cytokine release from endothelial cells and their subsequent influence on DDAH expression were investigated. In monocrotaline-induced pulmonary arterial hypertension in rats, the effects of inhaled tolafentrine on DDAH expression and activity were investigated. Real-time-polymerase chain reaction, immunocytochemistry, and PDE activity assays suggested high expression of PDE3 and PDE4 isoforms in endothelial cells. Treatment of endothelial cells with PDE3/4 inhibitor significantly decreased ADMA-induced apoptosis via a cAMP/PKA-dependent pathway by induction of DDAH2. Chronic nebulization of PDE3/4 inhibitor significantly attenuated monocrotaline-induced hemodynamic, gas exchange abnormalities, vascular remodeling, and right heart hypertrophy. Interestingly, PDE3/4 inhibitor treatment reduced ADMA and elevated nitric oxide/cGMP levels. Mechanistically, this could be attributed to direct modulatory effects of cAMP on the promoter region of DDAH2, which was consequently found to be increased in expression and activity. Furthermore, PDE3/4 inhibitor suppressed apoptosis in endothelial cells and increased vascularization in the lung.
  
  
  CONCLUSIONS
  Combined inhibition of PDE3 and 4 regresses development of pulmonary hypertension and promotes endothelial regeneration by modulating the ADMA-DDAH axis.
authors.affiliation: Max-Planck-Institute for Heart and Lung Research, Parkstrasse 1, 61231 Bad Nauheim, Germany.
authors.forename: Soni Savai
authors.initials: SS
authors.lastname: Pullamsetti
authors.forename: Rajkumar
authors.initials: R
authors.lastname: Savai
authors.forename: Martina Barbara
authors.initials: MB
authors.lastname: Schaefer
authors.forename: Jochen
authors.initials: J
authors.lastname: Wilhelm
authors.forename: Hossein Ardeschir
authors.initials: HA
authors.lastname: Ghofrani
authors.forename: Norbert
authors.initials: N
authors.lastname: Weissmann
authors.forename: Christian
authors.initials: C
authors.lastname: Schudt
authors.forename: Ingrid
authors.initials: I
authors.lastname: Fleming
authors.forename: Konstantin
authors.initials: K
authors.lastname: Mayer
authors.forename: James
authors.initials: J
authors.lastname: Leiper
authors.forename: Werner
authors.initials: W
authors.lastname: Seeger
authors.forename: Friedrich
authors.initials: F
authors.lastname: Grimminger
authors.forename: Ralph Theo
authors.initials: RT
authors.lastname: Schermuly
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000581:Amidohydrolases / Q000037:antagonists & inhibitors / Q000235:genetics; D017209:Apoptosis / Q000187:drug effects; D001120:Arginine / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000096:biosynthesis; D016207:Cytokines / Q000494:pharmacology; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D006976:Hypertension, Pulmonary / Q000188:drug therapy*; D009287:Naphthyridines / Q000494:pharmacology*; D009569:Nitric Oxide / Q000096:biosynthesis*; D010726:Phosphodiesterase Inhibitors; D011401:Promoter Regions, Genetic; D011659:Pulmonary Gas Exchange / Q000187:drug effects
chemical_list: D016207:Cytokines; D009287:Naphthyridines; D010726:Phosphodiesterase Inhibitors; C094030:tolafentrine; D009569:Nitric Oxide; C018524:N,N-dimethylarginine; D001120:Arginine; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D000581:Amidohydrolases; C059999:dimethylargininase; D006152:Cyclic GMP